In certain deep-drawing, stamping, and similar deformation operations with no material removal it is necessary to lubricate the zones of the sheet workpiece that are to be deformed, but at the same time those portions of the workpiece that are to be clamped must be left dry so that the workpiece does not slip when being worked on. The lubricant facilitates deformation of the workpiece by allowing it to slide on any dies or punches that engage it.
The traditional method of applying a pattern of lubricant to the workpiece is to spray the lubricant on. This procedure is fairly messy and entails considerable problems in containing the spray and controlling and treating the vapors generated by the sprays.
Accordingly German patent document 3,507,846 describes a system where the workpiece is passed in contact with applicator rollers having liquid-pervious coverings. The lubricant can be selectively fed to the interior of any of the rollers so that it passes out through the roller cover and wets the workpiece that is rolled under it, thereby producing a greased strip where a workpiece face engages a lubricant-filled roller, while the unfilled rollers leave the workpiece face fairly dry.
Such a system has two main disadvantages. First, the lubricant can normally only be applied in stripes extending parallel to the workpiece displacement direction. Even so when grease feed to a particular roller is stopped, the roller continues to apply lubricant to workpieces until its supply has been exhausted and the roller is substantially dry. Furthermore after feeding grease to a given roller it takes some time before it can apply a uniform coat to a workpiece engaging it. Thus if the striping is to be changed it is necessary to run several workpieces through the lubricator to clear out the residual grease before the new pattern will be applied accurately.
The second disadvantage is that there are invariably dry stripes left between adjacent rollers. The mounting equipment invariably takes up some room, so that there will inherently be voids between adjacent grease stripes on the workpiece.